The human skull, also known as the cranium, includes the face, mandible and head. Although there is debate as to the total number of bones in the human body, most experts agree that the skull typically includes 22 bones. The skull is nearly full size at birth, but the main bones in the configuration overlap and move to facilitate the birth process.
Function
The skull has flexible elements at birth that fuse as the body ages. The only part of the adult skull that moves is the mandible, also known as the jawbone. The skull protects the brain, defines the face, positions the eyes for stereoscopic vision, and permanently places the ears on each side. The skull is rigid due to the sutures between the bones that hold each in place.
Regions
The two major regions in the skull include the neurocranium and the viscerocranium. The neurocranium takes its name from the fact that it encloses the eyes, the middle ear, the olfactory bulbs for the nose, and the brain. The eyes, ear components and olfactory bulbs are not considered part of the skull. This region of the brain is divided further into a cranial vault and cranial base that hold the brain. These include a number of small bones that are made by endochondral ossification, a process of bone formation that begins with development of cartilage. The viscerocranium region of the skull includes the bones of the face, of which there are seven major types.
Development
The Center for Craniofacial Development and Disorders at Johns Hopkins Hospital notes that facial bone construction begins in the embryo at four to ten weeks of development. After the child is born and through the first year of life, the skull continues to develop. Changes in the skull occur throughout life, according to scientists working at the hospital. Genetics and environmental conditions, as well as disease and injury, can impact skull development at any age.
Features
The Anthropology Department at the University of California, Chico notes that skull bones include a number of "distinctive features" that allow easy identification. Doctors, anthropologists and scientists employ a universal notation system to identify the exact orientation and location of the bones. Specific terms, such as superior, posterior, lateral, and right and left, note exactly where on the skull a bone is located. Individual bones found in excavations by field anthropologists can be applied directly to a model of the skull.
Theories
Skull discoveries assist scientists in developing basic theories about the evolution of humans. Skull archaeological finds include the "Buhl Woman" discovered in Idaho in 1989, which is believed to be approximately 11,000 years old. The "Penon Woman III" skull, discovered in a Mexico City museum, was carbon-dated in 2002 to provide an estimated age of 12,7000 to 13,000 years. Study of the shape of the bones in the skull assists scientists in determining human migration patterns, according to Silvia Gonzalez, a geologist at John Moores University in England.
